146 THOMAS SAY FOUNDATION 



4. Subanal lobes of male very long and slender, and 



genital plate emarginate at tip -marlynia sp. now 

 Subanal lobes of male short and wider, female 

 subgenital plate not emarginate 5 



5. Head usually with a round yellow spot in front of 



the anterior ocellus ; knob on male eighth ab- 

 dominal sternite about as wide as long; male 



13-14 mm. long; female, 14-16 mm signata 



Head usually without a round yellow spot in front 

 of the anterior ocellus ; knob on male eighth ab- 

 dominal sternite wider than long; male 10-11 

 mm. long ventralis 



6. Color pale yellow to brownish ; female subgenital 



plate slightly produced and evenly rounded 



bell on a 



Color yellowish with brown markings on head 

 and pronotum 7 



7. Head mostly yellow, with no brown V-shaped 



mark connecting the ocelli 8 



Head with a brown V-shaped mark connecting 

 the ocelli 10 



8. Female subgenital plate produced over about 



half of the ninth sternite, with a slight emar- 



gination at the tip 5-punctata 



Female subgenital plate truncate, not produced- _ 9 



9. Males 13-15 mm. in length, females 14-16 mm.; 



area behind the ocelli usually brownish ; 2-3 cos- 

 tal crossveins beyond the end of subcosta 



sordida 



Males 10-11 mm. in length, females 11-12 mm.; 

 area behind the ocelli usually yellow; one costal 

 crossvein beyond the end of subcostal- -inarmona 



10. Subgenital plate of female triangularly produced 



over most of the ninth sternite ; subanal lobes 



of male bluntly pointed bilineata 



Subgenital plate of female broadly rounded ; sub- 

 anal lobes of male sharply pointed 11 



11. Male 11-13 mm. long, female 13-15 mm.; female 



subgenital plate almost truncate montana 



Male 10 mm. long, female 11-12 mm. ; female sub- 

 genital plate evenly rounded behind longiseta 



Isoperla f usca, new species. 



(Plate 2fi ? figs. 4, 5, 6.) 



Length to tip of wings, male, 9 mm. ; female, 10-11 mm, 

 Expanse, male, 16 mm. ; female, 18-20 mm. 



